diff --git a/src/Session.ts b/src/Session.ts
index c085726..6338522 100644
--- a/src/Session.ts
+++ b/src/Session.ts
@@ -55,6 +55,11 @@ export interface Party {
   recordings?: Recording[];
 }
 
+export interface Origin {
+  type:  'Call' | 'RingOut' | 'RingMe' | 'Conference' | 'GreetingsRecording' |
+    'VerificationCall' | 'TestCall';
+}
+
 export interface SessionData {
   id: string;
   extensionId: string;
@@ -64,6 +69,7 @@ export interface SessionData {
   creationTime: string;
   voiceCallToken?: string;
   sequence?: number;
+  origin: Origin;
 }
 
 export interface ForwardParams {
diff --git a/src/helper.ts b/src/helper.ts
new file mode 100644
index 0000000..2112f0f
--- /dev/null
+++ b/src/helper.ts
@@ -0,0 +1,50 @@
+
+import { Session, SessionData, Direction as callDirections } from './Session';
+
+function ringOutInboundLegCheck(newData: SessionData, allSessions: Session[]) {
+    const { parties = [], origin = { type: 'Call' } } = newData || {};
+    const party = parties[0];
+    const checkResult = {
+        isRingOutInboundLeg: false,
+        legSessionId: null,
+    };
+    if (!party || origin.type === 'Call' && party.direction === callDirections.outbound) {
+        return checkResult;
+    }
+    if (allSessions.length) {
+        for (const session of allSessions) {
+            const sessionIdGap = parseInt(newData.sessionId, 10) - parseInt(session.sessionId, 10);
+            const { party: existedSessionParty } = session;
+            switch (sessionIdGap) {
+                case 1000:
+                case 2000:
+                case 3000:
+                case 4000: {
+                    if (party.direction === callDirections.inbound && party.from && party.to &&
+                        existedSessionParty.from && existedSessionParty.to && (party.from.phoneNumber === existedSessionParty.to.phoneNumber) &&
+                        (party.to.phoneNumber === existedSessionParty.from.phoneNumber)) {
+                        checkResult.isRingOutInboundLeg = true;
+                    }
+                    break;
+                }
+                case -1000:
+                case -2000:
+                case -3000:
+                case -4000: {
+                    if (party.direction === callDirections.outbound && party.from && party.to &&
+                        existedSessionParty.from && existedSessionParty.to && (party.from.phoneNumber === existedSessionParty.to.phoneNumber) &&
+                        (party.to.phoneNumber === existedSessionParty.from.phoneNumber)) {
+                        checkResult.isRingOutInboundLeg = false;
+                        checkResult.legSessionId = session.id;
+                    }
+                    break;
+                }
+                default:
+                    break;
+            }
+        }
+    }
+    return checkResult;
+}
+
+export { ringOutInboundLegCheck };
diff --git a/src/index.ts b/src/index.ts
index 869e39f..8b2c070 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -3,7 +3,7 @@ import { SDK as RingCentralSDK } from '@ringcentral/sdk';
 import { Session, SessionData, PartyStatusCode } from './Session';
 import { formatParty } from './formatParty';
 import { USER_AGENT } from './userAgent';
-
+import { ringOutInboundLegCheck } from './helper';
 export interface SessionsMap {
   [key: string]: any;
 }
@@ -153,6 +153,15 @@ export class RingCentralCallControl extends EventEmitter {
       }
       // use first event's eventTime as session creationTime
       newData.creationTime = eventTime;
+      // if new session is the inbound leg of ringout call then abandon it
+      const checkResult = ringOutInboundLegCheck(newData, this.sessions);
+      if (checkResult.isRingOutInboundLeg) {
+        return;
+      }
+      if(!checkResult.isRingOutInboundLeg && checkResult.legSessionId) {
+        // if find an inbound leg then remove it from sessions
+        this._sessionsMap.delete(checkResult.legSessionId)
+      }
       const newSession = new Session(newData, this._sdk, this._accountLevel);
       newSession.on('status', () => {
         this.onSessionStatusUpdated(newSession);
@@ -170,7 +179,7 @@ export class RingCentralCallControl extends EventEmitter {
     }
   }
 
-  get sessions() {
+  get sessions(): Session[] {
     return Array.from(this._sessionsMap.values());
   }
 
diff --git a/tsconfig.json b/tsconfig.json
index 025d9fd..b5d71af 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -10,6 +10,6 @@
     "outDir": "lib",
     "resolveJsonModule": true
   },
-  "files": ["src/index.ts", "src/Session.ts", "src/formatParty.ts", "src/userAgent.ts"],
+  "files": ["src/index.ts", "src/Session.ts", "src/formatParty.ts", "src/userAgent.ts", "src/helper.ts"],
   "compileOnSave": true
 }